Answer:
The oldest rock being found at the highest elevation is primarily due to the geological process of mountain building or tectonic uplift.
During mountain building, tectonic plates collide, causing the land to uplift and fold. This process can bring older rock layers closer to the surface, or even expose them at the highest elevations. As the land is pushed upward, erosion occurs, causing the overlying layers to be removed, and the older rock layers to be exposed at the surface.
The physical characteristics of the bedrock that enable it to remain at the highest elevation during this process are its strength and resistance to erosion. The older rock layers are typically made up of harder and more resistant rock types, such as granite or metamorphic rocks, that are more resistant to weathering and erosion compared to younger sedimentary rocks.
As a result, the older and more resistant rock layers are able to withstand the effects of erosion and remain at the highest elevation. This is why the highest peaks of mountain ranges, such as the Himalayas or the Rocky Mountains, often consist of the oldest rock formations.